Speed presets using override 2 mode HVAC ACH550 + Bypass

Hi Flavio,

My name is Helmer, I'm working with an ABB VFD: HVAC ACH550 with an E-Clipse Bypass, I connected the drive to a FAN and I need to change its speed deppending of the temperature of a certain room. I want to change the speed trough speed presets.

Question is: In override 2 mode you have 2 reference source to change speed (param 1707) constant and PID, constant speed can only be change trough override frequency (param 1702) or can it be changed trough speed presets (param 1201) ?

Thanks for your time.

Regards.

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helmerRD Rank: 6423

Asked 2 years ago

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Hi Helmer

to obtain one regulation rpm / temp you can use much different methods.

First, your temperature sensor is ON/OFF relay or PT100 or thermocouple?

Depending on your sensore, you can use different approach.

For example, if you have ON/OFF temperaure relay with hysteresis, you can set different values in parameter 12.01. Of course in this case you have one approximate control of temperature.

If you have PT or thermocouple sensor, the sensor have analog output or not?

If yes, the solution is to connect the analog output of the sensor in input of PID drive macro, setting parameter 99.02 and successive to obtain the results desired.

The manual of ACH550 could give you other ideas to realize the automation that you need.
Last but not least, you can use supervision parameter in group 32, using the appropriate input and define one windows where activate one relay, with whose contacts active one fixed speed.

I can suggest you to try different methods and use what guarantees the best results with the minimum changes to your system.

Without other information about your project I can not give you more info

Hope this help you

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by helmerRD Rank: 6423 on 1/8/2018 6:44:28 AM | Like (0) | Report

Hi Flavio,

Responding your first question, I'm measuring the temperature though a PT100 connected to a PLC, and then using the PLC DOs to control the start of two fan depending on the temperature and to speed up at certain points.

A little bit more details about the project:

First FAN starts at 90F, once started stops at 85F.
Second FAN starts at 95F, once started stops at 90F.

First speed increase is at 93F. 50%
Second speed increase is at 97F. 75%
Third speed increase is at 100F. 100%

PD: FAN starts at 30% of maximum speed, and temperature ranges may change.

Is a ON/OFF control system, I would like to leave it like that, and not use a PID control, if its possible.

So as you see, is a simple project. Concerning to the drive:

parameter 99.02 is configured in 15 (E-Clipse) to switch between the Bypass and the Drive in Override 2 mode. So the Start command is given to the Bypass then it get to Override 2 mode and switchs to the VFD. But in override mode VFD ignores all DI except those concerning the override. So I can't use DI for presets speeds, only one internal preset that is specifically for override, 17.02 or 17.03. With the PID reference, I know that I can make speed changes even in override mode, but I don't have any Analog Output to control and I would like that to be my last resource.

summarizing:

1 - All I want to Do is to Start the Bypass, Change to the drive and the be capable to change speed with digital inputs.

2 - Honestly, this is my first time using an ABB VFD, and neither had used the Bypass concept before, so maybe I just not have the right idea, I want to clarify something:

I wire all the signal to the Bypass, and make the switch Bypass-VFD, so the Bypass is controlling the system and in case of a failure of VFD it switchs back to Bypass, that's how I understood that it should work. But if I wire signals to the VFD, in case of a VFD failure, can it automatically change to the Bypass too ? Because, in case of yes, that will solve my problems.

Sorry for the long message.
Thank you so much for your time.
Regards.

by Flavio Mussolin AKS expert

Rank: 4 on 1/8/2018 7:34:01 AM | Like (0) | Report

Hi Helmer
not all questions should require short messages...IMHO one good description of the problem could granted one better answer!

That said, I personally do not use the macro override. Generally this macro is used in U.S. and not in Eu....I prefer to work on the PID but you tell me that you can not.
If you can use PLC outputs to choose which constant speeds to use, I think it would be better

by helmerRD Rank: 6423 on 1/8/2018 7:52:33 AM | Like (0) | Report

Thanks for the words about the message, you are right.

About the override, I'm only using it because it was the only mode that I found that allowed me to change between Drive-Bypass. On the other part, Yes, I'm using PLC outputs to choose which constant speeds FAN's are going to have.

So if I send the start command to the drive, I can control the constant speed with the PLC outputs, we agree in that, but in case of a drive failure, does it will change automatically to the Bypass ?

Thanks.
Regards.

by Flavio Mussolin AKS expert

Rank: 4 on 1/8/2018 8:13:36 AM | Like (0) | Report

Hi Helmer

Override is one mode to use the motor without or in fault of the drive...if you have one PLC, you can use a dedicated FC to analize the normal funtioning of the drive. Start button, run drive, speed reach etc.
If the drive goes in fault, you can activate however by PLC the start of the motor with soft starter or Y/D connection, or DOL, you not wrote the power of the motor. The kW power?

Unfortunately I not have in my personal library an application same that you need.I do not have any other suggestions to give you at the moment

by helmerRD Rank: 6423 on 1/8/2018 10:08:53 AM | Like (0) | Report

Hi Flavio,

Motors power are 15 HP.

It's ok, my PLC application is already made and tested. My problem was with the drive, but I think that I'll figure out. I'm going to start the system trough the drive, then look for a way of provoking a fault in the drive to see if it automatically changes to Bypass, If I test that, I can guarantee my customer that motor will keep running even when the drive gets in fault condition.

Thank you so much for your time and help.
regards.

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Flavio Mussolin AKS expert

Rank: 4

Answered 2 years ago

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Speed presets using override 2 mode HVAC ACH550 + Bypass

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